The invention relates generally to marine seismic prospecting and more particularly to seismic streamer arrangements and methods for estimating the shapes of laterally steered streamers.
Seismic streamers towed by survey vessels and instrumented with hydrophones receiving seismic reflections are used in marine seismic surveys. The accuracy of the survey depends on an accurate estimate of the shape of each streamer. As the number of streamers towed behind survey vessels has increased, lateral-steering devices attached along the lengths of streamers are becoming a more common method of controlling streamer separations for more regular spatial sampling and for avoiding streamer entanglement. A known problem in estimating the shape of a laterally steered streamer is accounting for the local shape distortions caused by the lateral forces applied by the lateral-steering devices against the streamer. Typically, these devices kink the streamer, especially when applying a substantial lateral force to steer the streamer to port or starboard. The kink represents a discontinuity in the first derivative or the tangent to the streamer at the point on the streamer where the lateral force is applied. The magnitude of this local shape distortion increases as the tension in the streamer decreases toward its tail.
Thus, there is a need for better estimates of the shapes of laterally steered streamers.